<h2>DESCRIPTION</h2>

<em>v.extrude</em> creates faces, kernels or 3D lines based on input
2D vector features. Points are converted to 3D vertical lines, lines
to faces and areas to volumes (composition of closed set of faces and
kernel).

<p>
If <b>elevation</b> parameter is used then 3D vector features follow
the elevation model by using individual elevation values for the
vertices. Height for vertices is interpolated from elevation raster
map using given interpolation <b>method</b>.

<h2>NOTES</h2>

<em>v.extrude</em> extrudes vector features which means that points
are converted to vertical lines. Lines and area boundaries are
extruded to a set of faces, each segment defines one face. Area
centroids are written as kernels. Area as a composition of boundaries
and centroid is stored as a closed set of faces and kernel which
define a volume.

<p>
For conversion of 2D points or lines to 3D can be
used <em><a href="v.to.3d.html">v.to.3d</a></em>
or <em><a href="v.drape.html">v.drape</a></em>. In opposite
to <em>v.extrude</em>, these modules do not extrude vector features,
they defines z-coordinate for the features from given parameters or by
sampling elevation raster map values. It means that no feature type
conversion is applied, points remain still points in the output vector
map. Same applies for the lines.

<p>
<em>v.extrude</em> modifies only features geometry. Feature categories
remain untouched and attribute data is copied from input vector map to
the output.

<p>
By default, all features (including features without category) from
input vector map are processed (<b>layer=-1</b>). Feature selection
can be applied by <b>layer</b>, <b>cats</b> or <b>where</b>
parameter.

<h2>EXAMPLES</h2>

<h3>3D houses with fixed height</h3>

<div class="code"><pre>
v.extrude input=houses output=houses3D height=5 type=area
</pre></div>

<h3>3D houses with individual height</h3>

<div class="code"><pre>
v.extrude input=houses output=houses3D elevation=dem height_column=height type=area
</pre></div>

<h3>Convert 2D points to 3D vertical lines with fixed height</h3>

<div class="code"><pre>
v.extrude input=geodetic_pts output=points3D height=200 type=point
</pre></div>

<h2>SEE ALSO</h2>

<em>
<a href="v.transform.html">v.transform</a>,
<a href="v.drape.html">v.drape</a>,
<a href="v.to.3d.html">v.to.3d</a>
</em>

<p>
<em>
<a href="wxGUI.nviz.html">wxGUI 3D viewer</a>
</em>

<h2>AUTHORS</h2>

Jachym Cepicky,<br>
Updated for GRASS 7 by Martin Landa, FBK-irst,
Italy and Czech Technical University in Prague, Czech Republic

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